1. Field of the Invention
The present invention relates to a bearing which rotatably supports a main shaft or the like and a bearing apparatus which controls supply/discharge of lubrication oil for the bearing.
2. Description of the Related Art
In a conventional art, lubrication oil is supplied to a bearing which can rotatably support a main shaft in a housing to achieve lubrication so as to improve stability of a rotating operation or prevent the bearing from being damaged. In general, for example, an oil air scheme as described in Patent Document 1 is used.
[Patent Document] Japanese Unexamined Patent Publication No. 2001-90739
Here, a conventionally known bearing and a bearing apparatus which perform lubrication of the bearing will be described below with reference to FIG. 4. FIG. 4 is an explanatory diagram showing a conventional bearing 41 and a conventional bearing apparatus.
The bearing 41 which rotatably supports a main shaft 51 is an angular ball bearing which is conventionally known. A plurality of bearings 41 are attached along a shaft line of the main shaft 51 in a housing 52. In the housing 52, a supply path 42 which supplies oil air to the bearings 41, and a discharge path 43 to discharge the oil air from the bearings 41. In an oil air supply device (not shown), oil air is fed into the supply path 42 under pressure, and the oil air is supplied to be sprayed from a nozzle-shaped distal end of the supply path 42 onto an inner ring of each bearing 41 or a rolling element 41a. On the other hand, the supplied air and the lubrication oil are discharged from the discharge path 43 to the outside of the housing 52.
As described above, the conventional bearing apparatus performs lubrication of the bearings 41.
In recent years, a reduction in carbon dioxide emission for prevention of global warming is required, and development or the like of a technique which can reduce a consumption of lubrication oil is expected. In this case, even though lubrication oil supplied to a bearing is simply reduced, the bearing may be damaged due to a deficient amount of lubrication oil in the bearing. In contrast to this, when a predetermined amount of lubrication oil which does not cause a lack of lubrication oil in the bearing is periodically supplied, the lubrication oil may be oversupplied. For this reason, it cannot be desired to reduce an amount of consumption of lubrication oil, and heat is generated due to the oversupply to adversely affect machine accuracy of a machine tool. Therefore, an amount of lubrication oil in the bearing must be controlled to an appropriate level without excess and deficiency. However, in the bearing apparatus as described in Patent Document 1, since lubrication oil. (oil air) is supplied into each bearing 41 by being sprayed from the nozzle-shaped distal end of the supply path 42, an amount of lubrication oil apparently supplied into the bearing 41 would not be constant. Thus, an amount of lubrication oil in the bearing 41, in particular, on a rolling contact surface of the rolling element 41a cannot be easily controlled.